Oxidation of lower aliphatic alcohols



Aug. 19, 1947. D. c. Hum; ,8

I OXIDATION OF LOWER ALIPHATIC ALCOHOLS Filed July 8, 1944 I 6* I9 METER'n 5 P I 8 /CONDENSER STEAM I f 21 i 9 P I} SEPARATOR 24 ,-OXIDATION VUNIT Z I ,-PACKED 12 22v SCRUBBER RECEIVER y 2 RECEIVER .17 oxuuzmsMEDIUM DAWD L I HVVENTOR BY I fifln'w -bz ATT YS Patented Aug. 19, 1947OXIDATION OF LOWER ALIPHATIC ALCOHOLS David 0. Hull, Kingsport, Tenn,assignor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey Application July 8, 1944, Serial No. 543,999

6 Claims.

This invention relates to the direct oxidation of organic compounds,particularly the oxidation of hydroxy compounds such as lower aliphaticalcohols oxidized directly to acids.

As pointed out in my U. S. Patent No. 2,287,- 803 prior art oxidationprocesses have required the employment of relatively high temperaturessuch as 300 C. or 400 C. and the application of several steps. In otherWords, the oxidation either has not been direct, or if there has beendirect conversion, the yields have been very low. For example,considering prior art procedure for converting ethanol to acetic acid,before my invention it was considered necessary to first dehydrogenateall of the ethanol and thereafter the aldehyfiic dehydrogenation productwas converted to the acid which, as can be seen, involves a number ofsteps.

Carrying out oxidation processes in accordance with the prior artpossesses a number of disadvantages exemplified, for example, by therequired use of relatively high temperatures. Also there may in someinstances be the disadvantage of polymerization of the products and ofthe starting materials accompanied by low yields and other losses.

In my U. S. Patent No. 2,287,803 I have described a process for a moredirect oxidation of organiccompounds. While the process of my patentfunctions very satisfactorily and gives good yields in relatively fewsteps, it involves the utilization of metals having an atomic numberfrom 25 to 29. It is, therefore, apparent that it is desirable,particularly under present conditions, to develop a process in orderthat other metals may be employed and the process improved in otherrespects, as will be apparent from the description which follows.

After further investigation I have found that there are certain othercatalytic materials which may be employed in direct oxidation processesin a manner akin to the procedure set forth in my U. S. Patent 2,287,803which, not only permits obtaining direct oxidation, but permits theproduction of a relatively larger variety of products than hasheretofore been obtainable.

This invention has for one object to provide a process for the directoxidation of organic compounds. Another object is to provide a directoxidation process which is particularly valuable for the directconversion of lower aliphatic alcohols to lower aliphatic acids insubstantially a single step. Still another object, however, is toprovide a process which may be applied not only to the monohydroxyalcohols, but also to the polyh'ydroxy alcohols and similar organiccompounds. Another and particular object of this invention is to providea direct oxidation process which may be operated at relatively lowtemperatures and under ordinary pressure conditions,

yet give very satisfactory yields of the desired oxidation products.Still another object is to provide a direct oxidation process for theconversion of alcohols to acids wherein the alcohol may be converted,not only to an acid having a number of carbon atoms corresponding to thenumber of carbon atoms in the alcohol molecule, but also to a difierentacid. A still further object is to provide a process which may beoperated under other than normal atmospheric conditions; namely, undereither superatmospheric or reduced pressures.

A further object is to provide a direct oxidation process that may beapplied to either alcohols alone or mixtures of alcohols and aldehydes,or other types of mixtures. A still further object is to provide adirect, low-temperature oxidation process which may be applied tovarious mixtures of alcohols and aldehydes wherein both the alcohol andthe aldehyde are converted into useful oxidation products. Anotherobject is to provide a direct oxidation process, particularly adapted tothe treatment of alcohols such as butyl alcohol and the like wherein,not only may butyric acid be obtained, but contents of other acids.

A further object is to provide novel catalysts containing liquidsparticularly adapted for employment in the aforesaid types of processesfor the direct conversion of alcohols alone, or alcohols in variousadmixtures, into useful oxidation products. A still further object is toprovide methods for producing the catalysts as well as for activatingand utilizing the catalysts.

As already indicated, prior to my invention if an alcohol were to beoxidized it was generally first dehydrogenated and then thedehydrogenation products further treated. In any event prior artprocesses as applied to alcohols usually involve the utilization oftemperatures in excess of 300 C., which, not only requires substantialheat input but, due to the higher temperatures and other conditionsrequired in handling chemicals, yields of the desired end products arenot nearly as high as those obtained by my process.

I have found that contrary to such procedure an organic compound,exemplified in particular by a hydroxy compound as a lower aliphaticalcohol, may be directly oxidized at relatively low temperatures, eventemperatures substantially below C., with any of the usual oxidizingmediums of which the commonest one, namely air, may be readily utilizedin my process. Also my process, after it is placed in operation, doesnot usually require any heat input but generates sufficient heat itselfto maintain the reaction. Not only may single organic compounds betreated, but various mixtures of the organic compounds may be treated.For example, I have found that a mixture comprising a lower aliphaticalcohol,

together with a corresponding or a different aldehyde, may beefficiently treated by my novel process and catalyst to give very highyields of aliphatic acid. By my process and choice of catalyst it ispossible to obtain one or more acids in the oxidation procedure. Theforegoing features, as well as features of treating various mixturesunder different conditions, will be set forth in detail hereinafter.

While the oxidation procedure may be carried out in the apparatusdescribed in my U. S. Patent No. 2,287,803, for convenience ofconsideration and for a better understanding of the present inventionreference will be made to the attached drawing. The single figurethereof may be considered a semi-diagrammatic side elevation viewshowing a general apparatus arrangement which could be employed forcarrying out my process.

Referring to the drawing, 2 represents an oxidation unit which maycomprise any of several different constructions. For example, thepreferred external construction would, in a large diameter unit, be inaccordance with Hasche Patent 2,159,988. However, the construction maybe a sieve plate column, bubble plate column, or other comparablearrangement for permitting the contact of an oxidizing medium containingfree oxygen with the material to be oxidized. In the unit shown in theattached figure the column merely comprises an elongated, open column ofrelatively narrow dimensions. Attached to the lower part of the unit at3 and 4, are cooling jackets provided with inlets for cooling medium asat 6 and I.

The upper part of the unit was provided with a similar jacket 8;however, in this jacket, rather than cooling medium some heating mediummay be circulated in the event that high boiling components are beingdirectly oxidized or the reaction temperature is to be held lower thanthat which would maintain a constant volume of catalyst. Inasmuch as theconstruction is substantially the same, however, the mechanicalconstruction would be approximately the same and an inlet provided at 9,I and B; outlets are provided at ll, [2, and 13.

As indicated, if desired in place of the external jackets, coils may beincluded within the unit and in large-size units such arrangementwherein internal coils, or both coils and jackets are employed, may bedesirable.

The lower part of the unit is provided with a plurality of inletconduits, namely, inlet conduit [4 which is connected with atemperature-controlled feed supply [6. Also leading into the lower partof the unit is an inlet conduit 11 for oxidizing medium.

The upper part of the unit is provided with a drawoif conduit I8 whichleads throu h condenser l9 into separator 2|. This separator hasattached thereto a receiver 22 for condensate and a branch conduit 23through which noncondensables may be conducted to the scrubber Theaforementioned scrubber is provided with a receiver 26 at the lower partthereof and vent conduit 21 from the upper part thereof, which may leadthrough a meter or other device for measuring and testing the effluents.

There may also be associated with the apparatus thermometers or othertemperature controlling devices or various exchangers for recoveringheat or otherwise facilitating or rendering the operation of the processmore economica or permitting it to be operated with automatic control.Hence, my invention is not to be restricted in these respects.

I have found that certain metal compounds, as for example, salts derivedfrom the rare earth elements listed in the periodic table and includedin the group consisting of cerium, neodymium, lanthanum, praseodymium,illinium, samarium, holmium, europium, erbium, gadolinium, thulium,terbium, ytterbium, dysprosium, and lutecium, may be incorporated inacidic solutions and that these solutions will function as a catalystmedium for the direct oxidation of organic compounds. That is, analcohol alone or an alcohol and other organic compounds to be oxidized,may be passed into a catalyst solution, as aforelnentioned, in thepresence of an oxidizing medium containing free oxygen and the alcohol.may be directly oxidized to acid, as will be observable from thespecific data which follow.

In preparing catalyst solutions for use in the present process, anyconvenient source of the metal may be employed, such as salts, oxides,or other derivatives thereof. Preferably a derivative will be chosenwhich is is easily soluble under the conditions of the process. Forexample, assuming that it is desired to convert an aliphatic alcoholsuch as ethanol Or butanol directly to the corresponding aliphatic acid,the derivative of the catalyst metal may, for example, be a compoundsuch as cerium, neodymium, or other acetate, depending upon theparticular metal or metals employed. Further typical examples of metalderivatives which might be employed for producing the catalyst solutionare lanthanum acetate, terbium acetate, ytterbium acetate, dysprosiumacetate, and lutecium acetate.

While the aforementioned metal derivatives maybe employed in variousorganic liquids, which are solvents therefor, for simplicity ofoperation and minimizing the necessity of complicated separations, Iprefer to dissolve the catalyst compound in a liquid principallycomposed of one of the materials which is to be produced in the process.For example, in the event my process were to be applied in convertingbutyl alcohol directly into butyric acid I would preferably dissolve thecatalyst compound in an aliphatic acid such as butyric acid, although,propionic or acetic acid could also be used. However, for initiallypreparing the catalyst solution other liquids could be employed, as forexample, organic esters and the like such as butyl or ethyl acetate.

In any event, irrespective of the exact metal compound and the liquidthat the compound is dissolved in, the catalyst solution would be givena vigorous oxidation treatment such as blowing with a substantial amountof air, usually for a period of at least 5 or 10 minutes, and ifdesired, for several hours. This treatment would be accompanied by theintroduction of an aldehyde along with the oxidizing medium whichfunctions to convert the metal ions of the catalyst metal into a higherstate of valence than their lowest valencev The treatment may beaccompanied by heating obtained in any convenient manner, such as byflowing a heating medium in the jackets or coils in association with theoxidation unit or by introducing heated air. The temperature oftreatment, however, may vary from around 0 C. up to the boiling point ofthe particular liquid present. In other words the solution is maintainedunder liquid phase conditions.

It is also preferred to incorporate the oxidizing medium into thecatalyst liquid under at least atmospheric pressure as this permits theinclusion of a larger amount of oxidizing medium and fully saturates thecatalyst liquid.

After the catalyst liquid containing a rare earth metal compound asalready described has been treated and brought to a startingtemperature, usually above room temperature but below about 100 C., theorganic compound to be oxidized may be supplied to the process.

and to esters in addition to the main product of the oxidation, whilethe major portion of the remaining alcohol was left unchanged. Asindicated, while at normal atmospheric pressure, a temperature under 150C. appears to be quite satisfactory, the particular temperature selectedwill be determined largely by reference to the particular alcohol to beoxidized and whether the process is to be operated under pressure ormerely That is, referring to the attached drawing, the 10 at atmosphericpressure. oxidation column 2 is filled with thetkciatalysil; liquidUnder preferred operating conditions as, for fi p s e Or more rare earme a CO I example, when air is used as the oxidant, this pounds of thetype described dissolved in the 501- may be supplied under some pressureand, if devent and maintained at the desired temperature. sired, thsubstantial excess may be The y y p d to be OXidiZed is t 5 ployed,although for normal operations merely an zlizicedcinttg the ociliidationP590 58 t tll (fi i l excess is required that is, such an amount that aan 6 0X1 g me 111m, usua y a few per cent of oxygen will be present inthe h h p xy en 01' ozone m be pl y effluents. In the event of the useof other oxiand appear to render the catalyst solution more dants suchas relatively pure oxygen and ozone, active, but are not necessary), andthe compound smaner amounts are r quired and may be supoxidized 313 0 2mg geslljedfgxldatlon P plied under substantial pressure to cause them110 S, as W1 e 9501 e erema fully to permeate the entire catalystsolution.

Assuming that the oxidation product is a liquid, Th xid tion of anygiven alcohol in accorda portion thereofmay be volatilized or pumpedance it my process may be accomplished by fie'it iteilttii l32 3233352203???2 20? activating the i lg g the by means of a singe a e y e or b aluralit of lected in receiver 22. The unconsumed gases (as aldehydes'For example in oxigizing ethy1yal nitrogen when air is used as oxidizingmedium), 601101, I may employ acetaldehyde propionalde unoxidizedorganic compounds and the l1l e comhyde, or WWI-aldehyde alone or two ormore of Ponents, uncondensed: pass through conduit them. Moreover, I mayoxidize ethyl alcohol, 3322? iirttfiifififlii fai titiflldi'iltt alcoholbutyl alcohol or m1 alcohol, by employing any one or more of aldehydessuch as i ggigg gg f ggg lgfigs be employed or other acetaldehyde,propionaldehyde, butyraldehyde, The operation of my process to convertan or- F so :Iowever, t clh as acetaldehyde 1s ganic compound such asethyl alcohol, p-ropyl al- In many ances F reach aivallable and hascohol, butyl alcohol or other aliphatic hydroxy a 10W bollmg 110mb, Itwould pleferably be mcompounds to the desired acids and the functionployed along with alcohols $11011 as tyl 9 601101, of the various rareearth metals as aldehyde actiyl alcohol, and the like, as representingthe vated catalysts is quite clearly illustrated by the 40 mosteconomical procedure, as well as tending to data appearing in thefollowing table: lower the boiling points and permit the function-Percent Grams Percent E M t 1 M amgle g o a t S1511 Grams Alcohol FedofFlga kc. Yieclgigo Acid or Acids h 1A1 s90 94 100 HOA. iiiiij:ritfitita f? ??P $-Z 33g 9 A5. HOA

o 1', o [3- R IIIII 'o'iii ill'fiij 3, 870 fir niei itt yni 895 90.190%HOBu, 5% HOPI, 5% HOAc.

The foregoing examples were carried out in ing of the process at thelowest practical temperapparatus as indicated in the attached drawingatures. and at a temperature between 30 C. and Q, As already indicated,the pressure may be varalthou h a wider ran e of temperatures, such asied over wide limits without basically changing g g 50 C. to 150 C.could be employed satisfacthe process. However, since the processfunctorily. It will be observed from the above table tionssatisfactorily undernormal atmospheric that I have employed a relativelysmall amount pressures, I prefer to operate under such condiof the metalacetate in the catalyst solution in the tions. In some instances, suchas for saturating examples given, but this may be varied rather thecatalyst solution with oxygen, I may apply widely. For example, I mayuse anywhere from a few pounds pressure up to 2 or 3 atmospheres 1 or 2%of the metal acetate up to 12% or more.

While the foregoing examples are illustrative of preferred embodimentsof my invention, it will be evident that many modifications therein maybe made within the scope of the inventive concept involved and thatvarious other catalysts included within the group of rare earth metalsor compounds thereof may be employed. As previously indicated, thesecatalysts may be used under the conditions outlined above for theconversion of various aliphatic alcohols to acids. They may be employedin the form of a single salt or mixtures of salts of any desired organicacid or acids.

In the above examples, there was some small percentage of alcoholconverted to lower acids for this purpose. Also, as indicated, theprocess functions very well at temperatures of 5 C. to 50 or 70 C, andnormal atmospheric pressure. However, by raising the temperature abovethe range indicated to C., for example, the pressure should be increasedin order to assure a suflicient supply of aldehyde in the catalystsolution to obtain the desired catalyst activity. By operating at thesehigher temperatures and pressures, larger amounts of alcohol maybeconverted per pass per unit of time. Under such procedure the aldehydefeed would be correspondingly reduced as the amount of alcohol fed wasincreased. In general, it may be said that I prefer to carry out theprocess under liquid 7 phase conditions and at a temperature of 30 C. to70 C.

One valuable aspect of the present invention is that acids having fewercarbon atoms than the alcohol being oxidized may be directly produced,and the proportion of these other acids to the acid having the samenumber of carbon atoms as the alcohol being oxidized may be varied bychoice of the particular catalyst.

It is apparent from the foregoing that my invention is applicable to thedirect oxidation of the various organic compounds, particularly hydroxycompounds such as various alcohols. The foregoing data are merelyillustrative of some of the materials to which my low temperature liquidphase process may be applied, but various other compounds, such ashydroxy alcohols exemplifled by glycols, may be treated in a comparablemanner. Hence, I do not wish to be restricted in my invention exceptinsofar as is necessitated by the prior art and the spirit of theappended claims.

What I claim and desire to secure by Letters Patent of the United Statesis:

1. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a metal ion of a metal of the rare earth metal group in analiphatic acid with an aldehyde and a gaseous oxidizing medium to forman active catalyst solution, introducing material amounts of a loweraliphatic alcohol and a lower aliphatic aldehyde into the activatedcatalyst solution, oxidizing the alcohol of the resulting solution ofcatalyst, alcohol and aldehyde to the corresponding acid by treatingsaid solution with a gaseous oxidizing medium, maintaining thetemperature of the solution of catalyst, alcohol and aldehyde during itstreatment with the gaseous oxidizing medium such that the solution ismaintained in the liquid phase, and subsequently recovering thealiphatic acid produced.

2. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a metal ion of a metal of the rare earth metal group in analiphatic acid with an aldehyde and a gaseous oxidizing medium to forman active catalyst solution, introducing material amounts of a loweraliphatic alcohol and a lower aliphatic aldehyde into the activatedcatalyst solution, oxidizing the alcohol of the resulting solution ofcatalyst, alcohol and aldehyde to the corresponding acid by treatingsaid solution with a gaseous oxidizing medium, maintaining thetemperature of the solution of catalyst, alcohol and aldehyde during itstreatment with the gaseous oxidizing medium such that the solution ismaintained in the liquid phase at a temperature of from C. to 100 C.,and subsequently recovering the aliphatic acid produced.

3. The process of claim 2 in which the catalyst, alcohol and aldehyde ismaintained during its treatment with the gaseous oxidizing medium atatemperature of 30 C. to 70 C.

4. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a cerium salt in an aliphatic acid with an aldehyde and agaseous oxidizing medium to form an active catalyst solution,introducing material amounts of a lower aliphatic alcohol and a loweraliphatic aldehyde into the activated catalyst solution, oxidizing thealcohol of the resulting solution of catalyst, alcohol and aldehyde tothe corresponding acid by treating said solution with a gaseousoxidizing medium, maintaining the temperature of the solution ofcatalyst, alcohol and aldehyde during its treatment with the gaseousoxidizing medium such that the solution is maintained in the liquidphase at a temperature below C., and subsequently recovering thealiphatic acid produced.

5. A process for the direct oxidation of a lower aliphatic alcohol toobtain the corresponding aliphatic acid, which comprises treating asolution of a neodyminum salt in an aliphatic acid with an aldehyde anda gaseous oxidizing medium to form an active catalyst solution,introducing ma terial amounts of a lower aliphatic alcohol and a loweraliphatic aldehyde into the activated cata lyst solution, oxidizing thealcohol of the resulting solution of catalyst, alcohol and aldehyde tothe corresponding acid by treating said solution with a gaseousoxidizing medium, maintaining the temperature of the solution ofcatalyst, alcohol and aldehyde during its treatment with the gaseousoxidizing medium such that the solution is maintained in the liquidphase at a temperature below 100 C., and subsequently recovering thealiphatic acid produced.

6. A process for the direct oxidation of a lower aliphatic alcohol toobtain an acid mixture containing a major proportion of an acidcorresponding to the alcohol being oxidized and a minor proportion of anacid having a less number of carbon atoms than the alcohol, whichcomprises treating a solution of a metal ion of a metal of the rareearth metal group in an aliphatic acid with an aldehyde and a gaseousoxidizing medium to form an active catalyst solution, introducingmaterial amounts of a lower aliphatic alcohol and a lower aliphaticaldehyde into the activated catalyst solution, oxidizing the alcohol ofthe resulting solution of catalyst, alcohol and aldehyde to an acidmixture containing a major proportion of an acid corresponding to thealcohol being oxidized and a minor proportion of an acid having a lessnumber of carbon atoms than the alcohol by treating said solution with agaseous oxidizing medium, maintaining the temperature of the solution ofcatalyst, alcohol and aldehyde during its treatment with the gaseousoxidizing medium such that the solution is maintained in the liquidphase at a temperature of 5 C. to 100 C., and subsequently recoveringthe aliphatic acid produced.

DAVID C. HULL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,285,914 Drossbach June 9, 19422,263,607 Bludworth Nov. 25, 1941 2,287,803 Hull June 30, 1942 2,265,948Loder Dec. 9, 1941 FOREIGN PATENTS Number Country Date 111,050 AustraliaJuly 25, 1940

